1. Field of the Invention
The present invention relates to a transmitting apparatus, a receiving apparatus, and a method, and more particularly, to an apparatus and method for processing a digital transmission signal and a digital reception signal to correct an in-band gain flatness in a point-to-point communication system.
2. Description of the Related Art
Current communication systems are being developed in a way to transmit a greater amount of information, which requires a wider frequency band. Additionally, the communication systems increasingly adopt a modulation scheme with a higher frequency efficiency, for example a Quadrature Phase Shift Keying (QPSK) modulation scheme, an 8-Phase-shift Keying (PSK) modulation scheme, a 16 Quadrature Amplitude Modulation (QAM) scheme, instead of a conventional On-Off Keying (OOK) scheme used as a simple modulation scheme.
As a used frequency band becomes wider, it becomes increasingly difficult to maintain a constant in-band flatness in conventional communication systems using a high modulation scheme.
To solve the above problem, an equalizer is being used to correct the in-band flatness in the conventional communication systems. Typically, the equalizer may be used in a Digital Signal Processor (DSP) block of a receiver.
FIG. 1 is a diagram illustrating a frequency domain equalizer that is used in a conventional receiver.
Referring to FIG. 1, a signal received via an antenna may be converted into a baseband signal through a Radio Frequency (RF)/Intermediate Frequency (IF) circuit, and the baseband signal may be converted into a digital signal through an Analog-to-Digital Converter (ADC).
The digital signal into which the baseband signal is converted may be applied to a DSP module. The signal applied to the DSP module may be converted from a time domain signal to a frequency domain signal by passing through a Fast Fourier Transform (FFT) unit 101. The converted signal may be applied to a channel estimator 102 and a Frequency Domain Equalizer (FDE) 103.
The channel estimator 102 may estimate, based on the applied signal, an in-band flatness degradation signal that is generated while passing through a channel, and may apply the estimated signal to the FDE 103.
The FDE 103 may compare the signal applied to the FFT unit 101 with the signal applied to the channel estimator 102, and may apply a signal for correcting a difference between the two signals to an Inverse Discrete Fourier Transform (IDFT) unit 104.
The IDFT unit 104 may convert the corrected signal into a time domain signal, and may apply the converted time domain signal to a channel decoder 106. Here, the converted time domain signal may be sliced by a slicer 105, and may be applied to the channel decoder 106.
When an amount of information to be transferred by the equalizer of the general receiver is increased as described above, a required baseband frequency may be widened. In other words, a very fast FFT operation may be required.
However, in current systems having gigabit per second (Gbps) level communication similar to a millimeter wave band, it is very difficult to achieve the fast FFT operation even using a device technology enabling a high-speed operation, for example a field programmable gate array (FPGA).